1. Field of the Invention
The invention relates to range hoods that filter contaminated air.
2. Description of Related Art
Cooking on a grill or range typically produces an effluent stream of hot, contaminated air. The contaminants typically include particles, like soot or smoke; vapors, like oil and water vapors and volatile, odorous chemical compounds; and water droplets. Dealing with that contaminated effluent from the range is a problem, particularly in restaurants and other commercial and industrial settings in which the range is used for many hours each day.
The traditional method for dealing with the effluent from the range in industrial settings is to install a range hood over the range and other cooking appliances, and to connect that range hood via ductwork to a fan or blower, which is typically located on the roof of the building or at some other suitable point. The blower creates a pressure drop across the hood, causing the range effluent to be drawn into the hood and away from the cooking appliances.
Most range hoods have some type of filtration mechanism, either immediately within the hood or in a separate scrubber downstream of and above the hood. U.S. Pat. Nos. 4,266,569 and 4,281,635 to Gaylord are examples of typical filtration arrangements for a range hood. The hood/ventilators disclosed by those patents draw air through a highly tortuous path defined by a number of baffles, the idea being that the effluent stream will impact or impinge on the baffles, leaving behind any entrained contaminants, while the purified air stream moves on. In practice, this does not work very efficiently, and creates its own problems.
In fact, the typical filters and scrubbers, such as those described above, can be as little as 10-15% efficient. With that low efficiency, contaminants build up in the hood, scrubber, and ductwork. That build-up can cause reduced airflow and is a major fire hazard. Unfortunately, cleaning ducts is not a trivial undertaking—ducts typically require continual maintenance and cleaning, which incurs a high cost.
Range hoods that are more efficient in filtering the effluent stream from the range, and do so closer to the range, help to prevent contamination in the ductwork downstream from the hood. However, efficiency in filtering the effluent stream is not the only challenge in hood design. A good range hood is most advantageously efficient in filtering and removing contaminants, but it is also preferably designed to minimize internal contaminant buildup and to be easily accessed for cleaning and replacement of parts. With respect to easy access, even if access ports or doors are provided in the hood, if a hood is too tall or “high profile,” the components that most require cleaning may be too high above the workspace for easy access. In some cases, hood parts that most require cleaning or servicing may be above a drop ceiling and thus inaccessible without serious effort.
For example, U.S. Pat. No. 6,895,954 to Swierczyna et al. discloses a range hood in which the incoming contaminated effluent stream is forced to make a 180° turn into a water bath to strip some of the contaminants, after which it is forced to turn 180° again and is passed through a variety of filters, including a high-efficiency particulate air (HEPA) filter, before exiting the hood. Although the use of a water bath increases the efficiency of filtration, the tortuous air path makes it more likely that there will be a contaminant buildup within the hood itself, and the lack of easy access to the interior of the hood makes it difficult to deal with that contaminant buildup. Moreover, while a hood may attempt to direct the flow of effluent in a particular direction or through a particular series of turns, the effluent stream will take the path of least resistance, and it is thus possible that some of the stream will not travel through the water bath as intended. In the case of the Swierczyna hood, there is a gap between the water bath and the filter elements above it, making it possible that some of the effluent will bypass the filters.